I have Sonar Platinum with its attendant multiple plugins.
 
If I open Cakewalk many of those are missing although I believe if I already have them I should somehow be able to integrate them into the free CW. Is there an instruction on this?
 
Or do I just continue with Sonar Plat? Is it going to be upgraded any more, or is it gone beyond the version I now have?
 
Thanks for any help.

Absolutely leave Platinum installed and install Cakewalk by Bandlab alongside.

The VST paths should migrate but, just in case,  make sure the VST paths as defined in Cakewalk by Bandlab match exactly as defined in Platinum.

Note: The latest version of Platinum November 2017 and will not be updated.

Cakewalk by Bandlab is the was of the future as this will be continually updated - the latest being 2018.9 Build 29

A lot of my plugins didn't show up in CbB before I set it to run as an administrator, everything seems to be there now, give that a try if you haven't already

But some of the VSTS or plugs in Sonar Splat will NOT be in CWbyBL because they were paid for add ons by CW and since no more CW company, no more paid for limited edition plugs.
But yes you do have to check the folders in the VST scan. Not all of mine were shared properly.

If 64bit Platinum is installed ALL of the plug-ins bundled with it should show up in CbB. If the plug-ins do not appear CbB it is a problem with the scan path or a scan failure. Both of these issues are fixable. All of the plug-ins bundled with 64bit Platinum will work in CbB regardless of the manufacturer.

Wow! Thanks  guys. I am starting to understand the dynamics of CBD and Sonar. I had no idea of CDB until a couple of weeks ago, after a hiatus with Sonar.
 
I will check out paths and stuff and thanks for those hints, although I am realising there are more FX there than I first thought (in other words it may have worked), and that Dim Pro etc have a HEAP of instruments and FX of their own.
 
I wish life would stop getting in the way of the important stuff!