There are somethings you should be and should do in order to get likes. You should be above 18 years old on facebook to get likes. If you are not change your date of birth to above 18 years. The next thing is that you should allow followers on facebook to do this goto settings on facebook and allow followers. The final thing is that the privacy of the post on which you need likes should be public that is because you are getting likes from all around the world so in order to get likes from them your post should be visible in public.
Click here goto facebook and allow followers on facebook and before that change your date of birth to 18 above.
Go to your profile click on about then edit your profile and change your date of birth to above 18+ (use some logic)