The last time we won a game 3-0 was the last away game of the 22/23 season at Wycombe, so 28th April 2023, so nearly 22 months ago, or 79 games ago (off the top of my head). We also won 3-0 at Peterborough earlier that season.
The last time we won 3-0 at home? Answer is below, if you want to have a think first...
Walsall, 21st November 2020 - so 4 years, 3 months and counting.
But, in terms of other 3+ goal wins, we did beat Doncaster 4-0 on 5th March 2022, Harrogate 4-1 the day we lifted the L2 trophy, and Tranmere 4-0 on Good Friday a 5 weeks earlier.