Yet another migration from Mariner Paperless!

I am sorry to rehash this issue as I know that it has beed discussed many times before, but, in all honesty, I am relatively ignorant in any and all programing! I used Paperless to store all the receipts for my family as well as my shopping center business. On the business side, we have 3 sub-businesses and I had a separate database for each year for each sub-business. I had customized each receipt to record: Merchant, Paid Date, Amount, Payment Type, Check or EFT#, General Ledger Account #, Invoice Date, Category, Transaction ID and Account #, Common Area Maintenance (Y/N), Shopping center side, Store Name. I need to be able to search invoices by several different parameters, so I need all this information in each recorded invoice. It would also be ideal if I could total invoices by Category. I have dragged over to DEVONthink all of my invoices dating back to 2018. Each year of each sub-account is a separate database. On average, I have 400 to 750 invoices per year, I would like to create a template for future scanned and uploaded invoices. I would also like to find a way to convert the existing invoices into searchable records based on the above Paperless categories. I assume that there is no-one that can walk me through this, so where would you all recommend that I start to learn how to do this? I am not a total beginner, but I am not to far advanced from that so I will have to build my programming knowledge from the ground up! Sorry to be so long winded, but I am getting really nervous that Paperless will no longer function on my computer before I convert over to DEVONthink! Thanks!!!