Reddit mentions of Overstreet Comic Book Price Guide Volume 49: Batman’s Rogues Gallery

Unless there's a lot more this shouldn't be too bad...

Step 1 - Alphabetize. It looks pretty organized, that may already be done. Bags and boards too, nice!

Step 2 - Get yourself an Overstreet Price Guide. Other folks will point you to Ebay prices or online sources, but for 49 years, Overstreet has been the Bible for the industry and will tell you dates, creators, first appearances, etc.

https://www.amazon.com/Overstreet-Comic-Book-Price-Guide/dp/160360233X/ref=mp_s_a_1_2

Oh, cool! There's a digital edition now!

https://comics.ha.com/overstreet/comic-book-price-guide.s?ctrack=3482430&type=bodylink-1-comic--overst-48gen--tem071818

Step 3 - Learn how to make a spreadsheet. :) If you can't afford Microsoft Excel, that's fine, Libre Office can be downloaded for free.

https://www.libreoffice.org/

Make a catalog of what you have. Columns can be whatever you'd like, but the basics would be:

Title, Publisher, Issue #, Date, Cover Price, Notes, Price Guide Minimum and Maximum values (for insurance)

I also track Writer, Pencil Artist, Ink Artist so when a convention comes to town I can do a quick search for books to get signed.