Polygon to NURBS with Rhino5(64bit): Windows out of memory -> crash

Hi all,
really need some help.
Currently working on a project with a 360MB file, including a scan of a hand(polygonnet) and want to convert the hand from polygon to NURBS. Get the message “windows run out of memory” because the model has to many “sides”(more than 20000)
AMD Ryzen7 1700X
M2 Flashcarddrive 250GB, 500GB SSD as main drives + some other HDD
Graphic Card: NVIDIA GeForce 1070

I thought not to bad for this. But saw Rhino using up to 32GB of RAM and then crashing.
Any idea what i could do to avoid this?
I am quite new to CAD and all the “tricks” and “traps”. i recall there is a possibilty to tell Rhino to do calculations softwarewise or using hardwaresettings (?)
Could this be one mistake i did?

thanks for any tipp

Hello - MeshToNurb converts each polygon in a mesh to a three or four sided surface, it does not reverse engineer meshes to smooth surfaces - (https://wiki.mcneel.com/rhino/meshtonurb) there are no tools for that in Rhino other than expertise with the surfacing tools. There are some plug-ins that may help -