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

Here is Why You Need An Adapter

The outlet and plug type used in Yemen are A, D and G 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

Yemen

In Yemen, outlets of type A, D and G are in use.

Type A

Type D

Type G