You Do Need power plug adapter while traveling from Tajikistan to South Sudan.

Here is Why You Need An Adapter

The outlet and plug type used in South Sudan are C and D and in Tajikistan are C and F. This is how they look like.

Tajikistan

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

Type C

Type F

South Sudan

In South Sudan, outlets of type C and D are in use.

Type C

Type D