You Do Need power plug adapter while traveling from Guinea-Bissau to Liberia.

Here is Why You Need An Adapter

The outlet and plug type used in Liberia are A, B, C and F and in Guinea-Bissau is C. This is how they look like.

Guinea-Bissau

In Guinea-Bissau, outlets of type C are in use.

Type C

Liberia

In Liberia, outlets of type A, B, C and F are in use.

Type A

Type B

Type C

Type F