As you’ll find with most things in your RV, the first thing you’ve got to do is figure out the manufacture (brand)… and if able, the model before you can find support documents & parts you need.
Two of the most common awning brands these days are Dometic and Carefree of Colorado. I can’t help much with the first, but if it’s a Carefree… it’ll have a sticker somewhere on the roller like shown in the photos below. (NOTE: use the numbers on the roller sticker… not one on the fabric canopy (as shown on mine… it was a replacement)
From the sticker, you can find both the part number & serial number of your awning. From there you can either go to the Carefree website to identify which model awning you have, and then you can search for your part… or just call them with your info, and they’ll tell you what you need.