I found on youtube very helpful videos for 3a. They show all the basic mounts.
This video has all mounts and basic tricks for when the yoyo is spinning forward.
This video has all mounts and basic tricks for when the yoyo is spinning to the side.
These videos are more slower and probably better to learn all the mounts fully
This video Has almost all the mounts on the videos above, but is more faster. This video includes complicated tricks to demonstrate what these mounts can do.
Note: If you need me to tell you what the writing says, please PM me.