Get Label For SObject API Name

You can get the label using the DescribeSObjectResult:

DescribeSObjectResult describe = SObjectType.MyApiName__c;
system.debug(describe.getLabel());

Another common syntax is:

DescribeSObjectResult describe = MyApiName__c.sObjectType.getDescribe();

You can also just one-line it:

system.debug(SObjectType.MyApiName__c.getLabel());