Sources on the free web
The LawBod's collections of law reports for African countries varies considerably in strength & depth: you may well discover that for some countries the collection has an historic rather than a current emphasis.
Most reports of African cases are shelved in discrete collections according to the country of origin. All Nigerian law reports series will be alongside each other, & will have shelf marks including Nigeria.
However, in some instances, the decisions of African courts may have also attracted the attention of editors of comparative or international law or human rights law report series. These will have shelf marks starting General or Internat.
Please ask a member of staff to point you in the right direction!