Something like
MSCDEX /D:driver /L:letter
where ‘driver’ is the exact name for the driver you’ve used in CONFIG.SYS, and letter is the letter you want to assign to the first CDROM.
So for example if in CONFIG.SYS you’ve used VIDE-CDD.SYS like this:
DEVICEHIGH=C:\DOS\VIDE-CDD.SYS /D:IDECDROM
You would launch MSCDEX.EXE in AUTOEXEC like so:
LH C:\DOS\MSCDEX.EXE /D:IDECDROM /L:E
The drive letter is optional (I used E because this is what you told me about your CDROM drives in Windows). If you don’t specify the /L: switch, it will assign the first CDROM to the first available drive letter after all your hard disk partitions.