The whole, valid command would be (plus maybe some with-options)
RESTORE VERIFYONLY FROM DISK='\\SERVER1\Backup\my_big_db\FULL\SERVER1_my_big_db_FULL_20180803_210600.bak'
Sorry, but checking the disk space does not make any sense, since I do not specify, where I want to restore the database. It could be my local 128-GB SSD which would be never sufficient for a 500 GB database or it could be the 3 TB SAN drive. I could drop or overwrite the old database before executing the restore. I could increase the SAN-drive or could delete some old stuff...
God is real, unless declared integer.