Error For update to V5 For install the erpnext?

ikhlas3@ikhlas3:~/frappe-bench$ bench frappe --install_app erpnext sitev5
frappe app is not installed. Run the following command to install frappe
bench get-app frappe https://github.com/frappe/frappe.git
Traceback (most recent call last):
File “/usr/local/bin/bench”, line 9, in
load_entry_point(‘bench==0.1’, ‘console_scripts’, ‘bench’)()
File “/home/ikhlas3/bench-repo/bench/cli.py”, line 42, in cli
return old_frappe_cli()
File “/home/ikhlas3/bench-repo/bench/cli.py”, line 94, in old_frappe_cli
os.execv(f, [f] + sys.argv[2:])
OSError: [Errno 2] No such file or directory

Should be bench --site sitev5 install-app erpnext

Please check new bench commands bench --help

how to run the Bench after install the erpnext??I want to update my erpnext to V5…