Keeping inventory records as a self-employed person (hobby to secondary occupation)

Hello,

I have gone through the previous questions, but there are still a few that I do not fully understand.

I make soft toys, which was my hobby and has now become my secondary occupation, but I still have a lot of wool, filling and small parts (eyes, beads, ribbons, etc.), as well as crochet hooks.
I would like to enter these as inventory. I acknowledge that you have sale and user goods (purchase of goods and end products). How far back can this inventory be entered? I purchased a lot of inventory at least 5 to 6 years back. I have most of the receipts, but there are also regular purchases that have nothing to do with my secondary occupation. How should these be entered, as there is no vAT number? And some are from the EU.

Does this all have to be in one Excel file?

Thanks in advance!