Hello, Van Rooijen.
[echoing the response from SCALEHELP, in case it is helpful to other users]
The conversion can be performed with the AmpxMGFormat tool, as
AmpxMGFormat -i <input MG library> -o <output MG library> -f <desired format>
The desired format can be either "legacy" for the "old" format or "boff" for the most recent format.
Thank you,
Jordan