How to close resulting surfaces (or the mesh)

I used the MeshTrim command to get rid of the unneeded parts of my 3D-scanned object. I performed a QuadRemesh, but now i need to find a way to close the sides where I trimmed so i can use it for further analysis. I new to Rhino7, using it for my thesis.

Thank you!

without a file its a bit of a guessing game, since i dont know how the edges of your geometry look like. if that is the only hole to close you could try FillMeshHole click on one of the boundary edges on the Mesh. if there are more you could use FillMeshHoles. the results may look a bit weird but it should close it. if the right one is a polysurface that might be a pretty dens polysurface, is it maybe also mesh or subd? difficult to see from a small screen shot. if its subd you could try fill. if non helps post your file.

Thank you for your answer. I had already used the Fill command, but to get a good result a new QuadRemesh command was needed.