TOPIC: 10 track mono, how do I assign 1st 6 to surround

I have a 10 track ProRes feature supplied by a studio and I need to add to a timeline the first 6 tracks as surround. When I import the file my only audio options are 10 mono or 5 stereo. How can I ignore tracks 7 to 10 and group the first 6 as a surround L,R,C,Lfe,Ls,Rs
Turning off 7 to 10 does nothing the change the options.Dropping into a surround timeline with 7-10 off just makes all tracks into centre.
Am I missing something basic here?





Thanks in advance
Tony