My five-penn'orth.
From Nottingham station, walk with your bike to the R, cross Carrington Street via the pedestrian crossing, R then L descending to the canal. On reaching the canal, R and ride along the towpath, keeping your head low under bridges. This is intended as a calming stretch after your train journey! There's a sharp R at the basin, a short rise to London Road.
https://www.thebigwheel.org.uk/bigtrack/PDF/BigTrackDload.pdf
At sparrow-fart on Sunday you should be OK on the road S, crossing Trent Bridge and turning L along Radcliffe Road before the cricket ground, then R at the lights (A6011). After this excitement, you should be OK riding on the path at the side of the road, but certainly legal along the towpath on your L if you prefer.
After the towpath ends / big busy roundabouts appear, near
Regatta Way, there's a decent, if narrow, cycle path alongside the A52 as far as Radcliffe. I suggest leaving the path at the L turnoff at the RSPCA and riding through Radcliffe, rejoining the cycle path after riding straight on through the village (town?). It's just a bit more interesting, and avoids the nettles! The path is OKish as far as Saxondale interchange with the A46 - I'm not familiar with this bit, 'cos I normally reach the VoB via Gunthorpe Bridge. There should be signs? At any rate, from here past Bingham, there is NO cycle path alongside the A52, so go straight through Bingham to rejoin the A52 yon side. National cycle route 64 may be worth checking out? OK to Bottesford, then head to Long Bennington, Hougham, a bit of a climb via Gelston to Hough-on-the-Hill to join the A607 at Caythorpe, then N to Fulbeck.
The Cafe stop at Wymondham Windmill is highly recommended - fill your boots!
Don't write off Co-ops for vegan fodder; I've had some amazing bargains (like 85% reductions) at the one in Navenby, unfortunately N of your route, but surely available elsewhere in the mainly carnivorous backwoods.
Don't follow @talliman 's advice re Holme Pierrepont (the rest is OK!) unless you want to rebuild your bike - it's an interesting route if you like threading your way slowly through a maze of potholes in the unmaintained section, about a km, though it seems more. I'd be amazed if anyone can navigate a route through there without hitting a deep dip and dislodging bits of bike / fillings.
https://caffeveloverde.co.uk/ opens at 9, unfortunately for you! (Unless you're seriously behind schedule for Fulbeck!)
The cycle track alongside the A4
6 is loose stones in many parts, and slow / heavy going. Again, OK for a leisure ride, but not if you're on a tight schedule with your first audax to follow.
Good luck for your ride; at least the weather forecast looks good. Take care on the descents to Branston and the VoB, easy to reach 60km/hr, when things can happen in the blink of an eye.