What you are looking for is a Facebook.com “Like” Widget.
Facebook page like widgets are called Social Plugins. Using a Facebook Social Plugins page allows you to create widgets for Sharing, Liking, Following, Embedding, Comments and Activity of your Facebook Business Page or Facebook Group.
Make sure you have your Facebook page open, as you will need the link to your page to make a widget. If you don’t understand the options you are given when you hit the button to request the code, go with the iframe option. Using the iframe code will allow you to post it on your website or blog with ease.