Calibration QA sample size

Hello everyone. I am tasked with the inbound quality assurance on calibrations performed by 17025 accredited vendors for equipment used in our 17025 accredited labs. I am trying to determine the sample size to poll as a percentage of all inbound calibrations.

We perform somewhere between 4 and 5 thousand vendor calibration operations a year. I do not know the amount of previous failure rate, but I am looking to achieve accuracy of 3% with 95% confidence.

My background in statistics is somewhat limited, so I apologize if I am missing some information. What is the best way to statistically determine this (and why, so that I may learn).

Thank you for the help in advance!