How can I check google page rank?

[The Leader]

You can only see old PR on PR checkers as google as stopped updating them but they still use PR so keep going with the link building and the results will come.
Google stopped updating it so link builders would be put off when they can't see the PR changes.

 

[GilbertoL]

Google page ranking is dead. You can only track your keyword ranking. Here is a method to do that Pro Rank Tracker Review – proranktracker.com | Webtools Reviewed

 

[ZOH]

Check ahrefs.com.

You can use it to check page rank for your sites as well for a lot of more things. Their free plan includes a few checks per month, it should be enough to get what you need.