20평이라는 문자에서 숫자20만 추출하여 500을 곱해서 가격을 나타내고싶습니다. 어떻게 해야할까요?

from flask import Flask, render_template, request, jsonify
app = Flask(__name__)

from pymongo import MongoClient
import certifi
ca = certifi.where()
client = MongoClient('mongodb+srv://test:sparta@cluster0.qwdzo5h.mongodb.net/Cluster0?retryWrites=true&w=majority',tlsCAFile=ca)
db = client.dbsparta

@app.route('/')
def home():
   return render_template('index.html')

@app.route("/mars", methods=["POST"])
def mars_post():
    name_receive = request.form['name_give']
    address_receive = request.form['address_give']
    size_receive = request.form['size_give']
    price_receive = int(size_receive)*500


    doc = {
        'name': name_receive,
        'address': address_receive,
        'size': size_receive,
        'price': price_receive
    }

    db.orders.insert_one(doc)

    return jsonify({'msg': '주문 완료!'})

@app.route("/mars", methods=["GET"])
def mars_get():
    orders_list = list(db.orders.find({},{'_id':False}))
    return jsonify({'orders':orders_list})

if __name__ == '__main__':
   app.run('0.0.0.0', port=5000, debug=True)