One very important consider to keep in mind is that NCM 7.3 is the first release in which NCM will exclusively use the Orion Platform database. During upgrade, all NCM data is migrated from the existing NCM database to a schema in the Orion Platform database (which you are currently using for your NPM installation). As the upgrade happens, Orion Platform services are down; but they come up when upgrade is finished and while NCM data migration runs its course.
Check this compatibility matrix in planning your upgrades: Interspire Knowledge Manager Control Panel by SolarWinds
NPM 11.0.1 is the minimum version with which NCM 7.3.2 integrates.
NPM 10.7 is the minimum version with which NCM 7.3 integrates. So you would need to upgrade NPM to 10.7 before attempting to upgrade NCM to 7.3.
Your path would be:
Upgrade to NPM 11.0, and then upgrade to NCM 7.3.1
Upgrade to NPM 11.5, and then upgrade to NCM 7.3.2.