UNIX won't recognise DOS commands since it's UNIX and not DOS.
Under UNIX your quota can be checked by using the command 'quota'. This will display your current filesystem usage in the following way.
Disk quotas for user (XXXX) (uid XXX):
Filesystem blocks quota limit grace files quota limit grace
/usr 120 10000 10150 51 2000 2500
This report shows that currently 120K of 10MB of space is used for 51 of 2000 files.