You Do Need power plug adapter while traveling from Guinea to Bulgaria.

Here is Why You Need An Adapter

The outlet and plug type used in Bulgaria are C and F and in Guinea are C, F and K. This is how they look like.

Guinea

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

Type C

Type F

Type K

Bulgaria

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

Type C

Type F