If my PF usage in task manager is at 300 MB, does that mean I'm using 300 MB of my ram? If not, how can I see?

Yes, It depends on what type of computer you are using, But a Page file of 300mb is relatively small, my pagefile uses 1800mb of HDD space. a pagefile is hdd space allocated as Memory. If you have lag increase your Page File size under system properties to the allowed maximum recommendation. My page file is at 3000 mb

pf is page file (virtual memory) usage, that's a file that is basically reserved space on your hard drive. RAM usage is shown as "Physical Memory:...%" or click on the Performance tab and RAM usage is shown under "Memory" and "Physical Memory Usage History"