You Do Need power plug adapter while traveling from Guinea-Bissau to Myanmar (Burma).

Here is Why You Need An Adapter

The outlet and plug type used in Myanmar (Burma) are A, C, D, G and I 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

Myanmar (Burma)

In Myanmar (Burma), outlets of type A, C, D, G and I are in use.

Type A

Type C

Type D

Type G

Type I