Hi @kuoves, what is the file for? Only certain formats are applicable in studio for specific tasks. If you are importing meshes, you will need to convert the file into an (.obj) file.
If that wasn’t your question, send me a message and I’m sure I can help out!
Yes, try Doxillion or AVS Media Converter. Some of the conversion softwares convert only video files, unfortunately. I wouldn’t recommend free conversion softwares, just because the risk of your file being corrupted in the process is likely. if you do find one that works out though, stick with it.
Since your files are compressed, you will have to extract them first in order to import them into Roblox Studio.
I would personally just start using Blender, as it is a good software for 3D modeling, and it is generally simple to convert your file over to the file required to be imported into studio, mind me asking me what 3D modeling software you currently are using?