It depends upon which PIN you are referring to.
The IRS discontinued the use of the e-filing PIN. You will need to use your 2018 Adjusted Gross Income (AGI) instead. See the following links for more information.
If you have an 6 digit PIN from the IRS, this is used to verify your identity if you have been a victim identity theft in the past.
If you need to obtain your 6-digit PIN from the IRS, you will need to contact them.