I have fetch a temperature converter code from a GitHub repository. I want to show my calculated data history on screen whenever I press Convert button through shared preferences. Can anyone help me out?

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.green,
      ),
      home: TempApp(),
    );
  }
}

class TempApp extends StatefulWidget {
  @override
  TempState createState() => TempState();
}

class TempState extends State<TempApp> {
  double? input;
  double? output;
  bool? fOrC;
  late SharedPreferences prefs;

  @override
  void initState() {
    super.initState();
    input = 0.0;
    output = 0.0;
    fOrC = true;
  }

  @override
  Widget build(BuildContext context) {
    TextField inputField = TextField(
      keyboardType: TextInputType.number,
      onChanged: (str) {
        try {
          input = double.parse(str);
        } catch (e) {
          input = 0.0;
        }
      },
      decoration: InputDecoration(
        labelText:
            "Input a Value in ${fOrC == false ? "Fahrenheit" : "Celsius"}",
      ),
      textAlign: TextAlign.center,
    );

    AppBar appBar = AppBar(
      title: Text("Temperature Calculator"),
    );

    Container tempSwitch = Container(
      padding: EdgeInsets.all(15.0),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Text("Fahrenheit"),
          Radio<bool>(
              groupValue: fOrC,
              value: false,
              onChanged: (v) {
                setState(() {
                  fOrC = v;
                });
              }),
          Text("Celsius"),
          Radio<bool>(
              groupValue: fOrC,
              value: true,
              onChanged: (v) {
                setState(() {
                  fOrC = v;
                });
              }),
          SizedBox(
            height: 90,
          )
        ],
      ),
    );

    Container calcBtn = Container(
      child: ElevatedButton(
        style: ElevatedButton.styleFrom(
            minimumSize: const Size(200, 50),
            maximumSize: const Size(200, 50),
            textStyle: const TextStyle(fontSize: 20)),
        child: Text("Convert"),
        onPressed: () {

          setState(() {
            fOrC == false
                ? output = (input! - 32) * (5 / 9)
                : output = (input! * 9 / 5) + 32;
          });
          AlertDialog dialog = AlertDialog(
            content: fOrC == false
                ? Text(
                    "${input?.toStringAsFixed(2)} F : ${output?.toStringAsFixed(2)} C")
                : Text(
                    "${input?.toStringAsFixed(2)} C : ${output?.toStringAsFixed(2)} F"),
          );
          showDialog(builder: (context) => dialog, context: context);
          print('output');
          print('input');
        },
      ),
    );

    return Scaffold(
      appBar: appBar,
      body: Container(
        padding: EdgeInsets.all(16.0),
        child: Column(
          children: <Widget>[
            inputField,
            tempSwitch,
            calcBtn,
          ],
        ),
      ),
    );
  }
}

I tried of getting string value but I don't understand that how to get read and save data of user input? I am expecting to have a calculated data on screen with input and result data whenever I press the Convert button.