Make sure that enough space is available in order to be able to start the import process (bottom right button). Notice in the bottom left it will show you the required disk space. You can choose to import/don't import individual archives via the toggle on the left. Vortex will now display a list of all the mod archives it has found. Depending on the amount of mod archives you have, this might take a few seconds. Vortex will now look up the mod archives by scanning NMM's cache information. Once you are ready to proceed, click 'Next' in the bottom right. Note: you will have to go through any mod installers again and select the options you want and Vortex will reorder your plugin load order automatically. Once imported, you will have the choice to install the mods anew, or leave them uninstalled for now (if you want to install the mods at a later point in time instead).

Most notably, this import tool will only import mod archives.

Please make note of the information provided on this step informing you of the limits of the import process. The first step will allow you to pick the NMM installation you want to import mod archives from - in case you have more than one instance of NMM installed. The import process is broken down into several steps. To do so, switch to the mods view (side panel > Mods), click on 'Import From.' and select 'Import from NMM'. Vortex gives you the ability to import your mod archives from an existing Nexus Mod Manager installation. Note: Importing Mods from NMM - applies to Vortex 1.0.0 and later.

Nexus mod manager mod list