You Do Need power plug adapter while traveling from Slovenia to Tokelau.

Here is Why You Need An Adapter

The outlet and plug type used in Tokelau is I and in Slovenia are C and F. This is how they look like.

Slovenia

In Slovenia, outlets of type C and F are in use.

Type C

Type F

Tokelau

In Tokelau, outlets of type I are in use.

Type I