What is the difference from Intapersonal skills and Inter personal skills?

Intra means within.

Inter means between.

Inter-school football matches mean football matches between schools.  Intra-school matches are within a particular school, perhaps between different houses of the school.  ("The intra-school matches were an inter-house competition.")

Intrapersonal skills are skills for managing yourself.

Interpersonal skills are skills for relating to other people.

Both intra and inter are from the Latin.