If that printer has the hard glass surface, I use a razor blade and work it under a corner, and then gently work it around the perimeter until it releases. Some glue stick on the surface before you print helps as well.
Here's something you can do, on Tinkercad, look thru the gallery section, you might find a pulley there that meets your needs, you can copy it or you can select "tinker this" and manipulate it to what you want, I have been able to re-work file from Thingyverse, I just import it to Tinkercad and instead of manipulating it in the original file, I add to the file and make my own file out of it, if that makes sense, don't get frustrated, it's easier than you think, you just need to play with it and find what does what... then ask us again and again and again, that's about it...