The bearings are inside the seals so run on the same oil as the hub, which hopefully you’ve been changing regularly!
It’s really easy to open it up for a look-see. Take off brake rotor (if fitted), take off gear selector arm, take off drive cog (behind a snapring). Then remove the locknut and cone completely from the non-driveside (17 and 15mm cone spanners), and open the driveside by turning (by hand) the big knurled plastic ring which unscrews clockwise (might be behind another plastic cover which pulls off). The guts of the hub will come out in one go for inspection.
Plenty of help and pictures already online eg https://hubstripping.wordpress.com/2010/02/03/11-speed-alfine-hub-from-shimano/ you can see the bearings in the photo