16.5 SiP Layout XL includes menu items for importing and exporting MCM databases from SIP. They are located at:
File -> Export -> MCM and File -> Import -> MCM
If you don't see these, then you may have an old menu file, you may have modified your menu files unintentionally, etc. The commands are "mcm export" and "mcm import", respectively, from the command line. Hope that helps. If you're using a non-layout SIP tool, such as the SI product or the architect tool, I do not know that these include this capability. Note that there is data loss in the conversion, of course, since you are moving to a lower-tiered tool with less functionality (such as lack of die stacks, spacers, interposers, etc).