If you transferred last year’s tax data to this year's return, your state and local refunds are automatically brought over with your other tax info.
Also, your state/locality may have sent you a 1099-G form, if they haven’t gone paperless. You should receive your 1099-G by mid-February if your state/locality still sends out paper forms. If you did get a 1099-G, make sure it's for a state/local tax refund, not unemployment compensation.
Here are some other places you might find the amount of last year’s state/local refund:
Last year's state tax return
Your bank statement showing your entire state/locality refund