You have to give Amazon what they ask for. You said it has been awhile since you bought these items which means it might take some digging to find your invoices/receipts for them and to track your purchase from source, through prep and shipping to Amazon etc. Your only other choice is to stop selling on Amazon as they’re going to keep you shut down until you provide the documentation. Good luck!

If I can find the receipt, will they accept it

When you say that, I track it through prep and shipping to Amazon. Is it through the Prep Center