Arm muscles are roughly divided into forearm muscles, biceps and triceps;

Forearm exercises with dumbbells are: forehand grip, forehand grip and reverse grip;

Biceps exercises with dumbbells include: dumbbell alternating bending, dumbbell Scott bending and dumbbell concentrated bending;

Using dumbbells to exercise triceps include: double-arm dumbbell neck back arm flexion and extension, single-arm dumbbell neck back arm flexion and extension, dumbbell bending arm flexion and extension.

As for how to do these movements with dumbbells, you can refer to the contents of Stallone's core lecture, which is very detailed.