even when I convert my file to a format that Mega accepts, erros keep occuring.
This is not very helpful. For example, what format did you try, how did you convert it, and what was the error?
IQ-TREE makes lots of different files. What you need is one that ends in
.contree, which is a consensus tree in Newick format. If you don't have that file, another one that should work ends in
.treefile, also in Newick format. Neither of those two files requires conversion for MEGA, but you may need to rename them so they end in
cp something.contree something.nwk
Now you should be able to open
something.nwk in MEGA without problems.