https://support.juniper.net/support/downloads/
.img file for Media installation ( USB )
.tgz for Package installation ( using request cmd and file in /var/tmp/ )
1- check the version and HW >>>> this one is a VC and use -qfx5e- release
https://www.juniper.net/documentation/en_US/junos/topics/concept/junos-flex-overview.html
2- allow root-login
set system services ssh root-login allow
set virtual-chassis no-split-detection
3- copy the file to the QFX and do an ISSU upgrade
request system software add /var/tmp/jinstall-host-qfx-5e-x86-64-18.3R1.9-secure-signed.tgz
request system reboot