Is there a way to find the grams and dimensions for an STL file?

Use the (Free) CAD Assistant application. Once you open the file (you may need to turn on mesh files from the filters), there is the Model Browser option. Select the body and then on the right, you can get the assembly properties (Ctrl+I). You'll get bounding box size and Volume, the two you are interested in. The Volume will give you weight (mass) once you multiply it by the material density of whatever material the body represents. Without knowing density, you can only get volume... Beware of the (linear) scale perhaps being off by a factor of 10, 100, 1000 or 2.54 (or 2.54*12, etc.) depending on what units the original file used and what the viewer provides. If you need more information, I suggest you post the file, more information and have someone provide those values for you...

You can download MiniMagics(Free Tool) to inspect STL files. It will show you the dimesions and other infos like in the screenshot. With just 1 click.

https://www.materialise.com/en/software/minimagics

sent it to Simscape-multibody in Matlab software.