I'm new to 3d printing and i'm trying to learn and print useful items as a part of my learning. 

I was able to print this for practicing and it came our well for my first try https://www.printables.com/model/813314-carpuride-w702-to-quadlock-receiver-adaptor. 

I wanted to remix https://www.printables.com/model/813314-carpuride-w702-to-quadlock-receiver-adaptor & https://www.printables.com/model/1175107-garmin-zumo-xt-handlebar-mount i.e., cut the legs on https://www.printables.com/model/813314-carpuride-w702-to-quadlock-receiver-adaptor and merge it with one of the mesh body and align the screw holes. 

I tried doing some trial & error with Fusion 360 but I'm not able to delete any pieces or copy from other model.  Can someone help me with this?