Windows 10 update

Hiya, 

I was trying to shed some light on a not issue we are having but trying to get my head around,

I work for a company and we have a selection of Dell Pcs,

Optiplex 3010, 3020, 3040, 790, 7020, 780, 7010, 9020 

XPS - 8700,

Alienware - Aurora-R4, 

We know the windows 10 free upgrade has passed, we have upgraded a few recently and they have activated from windows 7 pro, 

are these covered in a dell OEM  licence 

Thanks

Rich