Digital Files for Etsy in multiple sizes at 300 DPI

I need help with converting my files to be suitable for customers to download and print on Etsy in multiple sizes, I have saved them incorrectly and need them reviewing and sorting as I have done something wrong. They will need to be corrected to 300 DPI , they were created in Procreate correctly and then shared in Canva which is where an error has occurred , there are over 50 to sort and I will need to know how to manage the files in the future , I’m looking for a UK based freelancer who can get this sorted and help me move my Etsy store forward, as soon as possible at a sensible price , many thanks