UK number plates include an "age identifier": two digits that show roughly when the car was first registered. New identifiers are issued twice a year, in March and September.
A 74 plate is the September 2024 batch, covering registrations from 1 September 2024 to the end of February 2025. The number works by taking the last two digits of the year and adding 50 for the September batch (24 + 50 = 74) - the March batch that same year would have been a plain 24 plate.
This tells you the age band the car falls into, not its exact registration date. If you want the precise date, that's on the vehicle's own registration record rather than the plate.