"Thank you. I'm not sure of the model either, it is 21' if that helps any."
The trailer "model number" is located two places on your trailer. First is a decal, usually located by the front entry door and the other location is on the weight certification decal that's located on the roadside front corner of the trailer.
If both of those are missing, if you can find a brochure from that year or from a close to that year and brand, you can compare floorplans to usually come up with the model number.
Failing that, with the VIN, you can call Keystone RV at (866) 425-4369 or send them an email from their website:
https://www.keystonerv.com/contact-us and provide them the VIN. They will give you the model, date of manufacture and can provide quite a bit of additional information about the trailer "when it left the factory"... They cannot provide any "trailer history" such as repairs, maintenance or ownership...
Here's examples of both. In the top one, the trailer is a Cougar 34TSB and in the second, it's a Cruiser XT-245