You can refer below links on some details on moving server from VRTX to M100e. The key difference is blade on VRTX chassis will have Bridge cards on Mezzanine slot where M1000e need Mezzanine cards and Mezzanine slot and we also need to ensure there is no fabric mismatch [URL] [URL] 
Hello, We are in the midst of retiring our Dell VRTX chassis.  With that, we would like to move our blades to our M1000e chassis.  Are there any hardware changes that need to be made for that to work?  I see documentation about moving blades from an M1000 to a VRTX, but not the other way around.   Any help would be greatly appericated. Thanks.
Dell VRTX M620 Blade to M1000e Chassis