Your 1m x 1.5m print has a resolution. If this were dpi, you could have 39.3in x 59.6in, and if that were 300 dpi, then it would be 11790px x 17880px. So, if you wanted to print at 300dpi, you basically need an image of 210,805,200 or 210 megapixels.

300dpi is the quality of most 5x7 or 8x10 photo prints.

Most large prints are not 300dpi. But this gives you an idea of your process. Find what resolution your large print can be printed at, and do some calculations to determine the ideal resolution to scan your film at.

The optimum scan resolution for 35mm [may be 3200dpi][1]. You are correct that the film's grain size will cause a limit to the scan resolutions that are reasonable.

[1]: https://x-equals.com/film-to-digital-scanning-essentials-101-part-1-of-2/#:~:text=If%20scanning%2035mm%20(also%20known,detail%2C%20just%20making%20more%20pixels.

Your 1m x 1.5m print has a resolution. If this were dpi, you could have 39.3in x 59.6in, and if that were 300 dpi, then it would be 11790px x 17880px. So, if you wanted to print at 300dpi, you basically need an image of 210,805,200 or 210 megapixels.

300dpi is the quality of most 5x7 or 8x10 photo prints.

Most large prints are not 300dpi. But this gives you an idea of your process. Find what resolution your large print can be printed at, and do some calculations to determine the ideal resolution to scan your film at.

The optimum scan resolution for 35mm may be 3200dpi. You are correct that the film's grain size will cause a limit to the scan resolutions that are reasonable.