you can check youtube with keywords, pencil grip.
We call it the tripod grip (using your fingers and thumb).
The Basic Tripod Grip - Using The Basic Tripod Grip
I'm a therapist. I've seen many kids write with unusual grips. The ones with the most difficulties are those who also have reading or spelling difficulties. Bad handwriting takes some time to correct if the child already in primary school.
Rubber or silicone pencil grips only work for some kids. Triangular pencils & fat pencils work for more kids.
hope this helps!