How can I find the form ID of a form?
Finding FORM ID without installing module

Finding the Form ID is very easy no need to install modules and all 

STEP 1: Open you from go to its edit page(OR inspect your form).

STEP 2: if its a node form find "node-form" in the inspect element

 check you are in the form element.

STEP 3: see attached image the highlighted green text is the ID of the form 

STEP 4: IMPORTANT Finally if you want to use it in hook_form_alter() replace the hypen with underscore

For example: yourform_id_with_content_type_name_form

Like wise you can find id of any form in drupal all you have to do is inspect->find form element and search for the ID attribute and use it 

Hope it helps :)