It says K1 and K2 are the tacho signal ie a DC voltage proportional to speed. I doubt that will be any use with modern drives.

I have similar SEM motors on my Shizuoka mill with Centroid Acorn controller and drive them with a CNCdrive.com driver. However, these use step/dir for position control so wouldn't be much use to you https://cncdrive.com/downloads/DG4S_series_manual.pdf

I suspect you might be better off using a modern servo drive that takes a direct (isolated) 0-10V analogue signal among other optional inputs. They can usually be configured for speed or position control. I have used Yaskawa servos previously but also Lichuan servos as suggested by Jazz, which are more cost effective.