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

Here is Why You Need An Adapter

The outlet and plug type used in Yemen are A, D and G and in Syria are C, E and L. This is how they look like.

Syria

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

Type C

Type E

Type L

Yemen

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

Type A

Type D

Type G