MO2 and NMM are not "connected". They both have access to the plugins list and can both enable and disable them. But only the manager that installed the mod can uninstall, reinstall or modify that mod.
Moving from NMM to MO2
1. Locate NMM's "downloads" folder (if it has one). Should be a folder where it stores the downloaded files.
2. Access MO2's downloads folder:
At the top, above the priority window in the middle is an icon with an open folder on it. Click on this and select "Open downloads folder" from the drop down menu. This will open a File Explorer (Win 10) / Windows Explorer (Win 7) window at the downloads folder location.
3. Move NMM's downloads files (7z, zip, rar) to MO2's "downloads" folder.
4. Uninstall all mods from NMM
5. Make Skyrim Vanilla Again:
This is needed in order to get rid of anything left over.
6. Start game up without mods, to ensure any INIs get properly created.
7. Install the mods in MO2
Go to the Downloads tab on the right hand side
Right click an entry and choose Install
Or double left click
8. Install any mods that need to be manually installed in the main game folder (i.e. SKSE64)
NOTE: You do not need to be concerned about the order of installation. You can instead change the priority order by moving mods up and down the list on the left hand side. Furthermore, if you do not remember the installation order when installed with NMM and have a different priority order in MO2, there is a good chance that your save games may not function or appear as intended. New game recommended.
Disconnecting NMM and Connecting MO2
Do the above and MO2 will be connected and NMM can be uninstalled.