Mounting a NFS (or other) filesystem and mounting an ISO image are two separate issues. You appear to already know how to mount the NFS filesystem. Once you've done that, then the ISO image is just a file there -- so now you mount that *.iso using the method outlined above.
The reason you got the error
192.168.0.100:/mnt/inst/disk1.iso: No such file or directory
is because you were trying to mix the mounting of the NFS share and the ISO image in one command. Therefore, there was no file to be mounted. Mount the NFS filesystem first, then mount the ISO image.