Here are the exchanges with the list of symbols:
https://www.barchart.com/futures/prices-by-exchange
Futures Contracts Months https://www.cmegroup.com/month-codes.html
If you are trading S&P Eminis the symbols for 2023/2024:
[ES+contract month+year]
March H: ESH4
June M: ESM4
September U: ESU3
December Z: ESZ3