You Do Need power plug adapter while traveling from Grenada to Tahiti.

Here is Why You Need An Adapter

The outlet and plug type used in Tahiti are C and E and in Grenada is G. This is how they look like.

Grenada

In Grenada, outlets of type G are in use.

Type G

Tahiti

In Tahiti, outlets of type C and E are in use.

Type C

Type E