How to solve my situation of having several Mac users created for me as I used Migration Assistant multiple times to move files from my PC

I recently tried to migrate data from my old and perpetually unstable PC to my new iMac through the Set up Assistant. However, half way through the 6 hour process, my PC crashed (the exact reason why I finally bought a Mac!) and the connection was lost. I continued with the Mac set up and then tried again later to migrate the files with Migration Assistant. Since I was nervous that my PC would crash again, I decided to do the data transfer in multiple migrations (ie. first I did photos and then after seeing that that was done successfully I did music and so on). Unexpected to me, even though all of the 4 migrations were successful I now have 4 additional users (in addition to the one I set up durnig the initial process) because each migration created a new user. Each user has little bits of my data.

What is the easiest way to merge these users or at least the data that resides in each one? I really only want one user. thank you.