In reply to JB:
I run a drum scanning service where we can drum scan to 6000dpi but I wouldn't recommend it for a print. The maximum I'd try with a print is 2000dpi but we can put it on our Fuji Lanovia flatbed and scan at 2000-3000dpi to give you decent enough result to blow up to what you want and maybe bigger.
I'll also do it as part of a free trial for you so if you want to send to http://drumscanning.co.uk up in the Highlands, we can send you the scan of it back via wetransfer. Just use special delivery, we've never had a letter go missing using this service. We'll let you know the cost for return and send you a Paypal invoice.
It would be interesting if you post the final scan here too!
Tim Parkin
p.s. If you're interested in the resolution of film here's a fascinating PDF
https://www.tmax100.com/photo/pdf/film.pdf
Elsehwere I've found colour photographic paper limiting resolution is approx 65 line pairs per mm which is about 3000dpi but you'll have so many losses in enlarging etc that 2000 would probably be the limit and most photographs would achieve substantially less than this
Post edited at 23:18