If I am a 8 year FO and upgrade to captain, will i be on year one or year 8 of the CA payscale?

Sorry, I'm new.

Depends on the specific company. The industry standard is that pay is based on date of hire, however at a former employer, it was date of upgrade, and your time of service was re-set to 0 for pay purposes. I know of a few other airlines where this was the policy, but they are in the minority, by far.

In the US at least almost all airlines you'd be on 8th yr CA pay. It used to be at several places they'd reset you to year 1 CA pay but it's not a problem these days.

In the US, year 8.

Most other countries, year one.