I need to make mandatory Incorporation State/Province based on Incorporation Country. If Incorporation Country is Unites States or Canada The Incorporation State should be mandatory.
Try using a
Validation Rule. You need it to return true when there should be an error, so its syntax should just check for either value, paired with a blank state.
AND( OR( Incorporation_Country_Text__c = "Unites States", Incorporation_Country_Text__c = "Canada" ), ISBLANK(Incorporation_State_Province_Text__c) )