Hello sothb,
As long as you have connection to the EX9200(make sure you don't have a firewall filter blocking destination port 22 and 23 - otherwise you have allow your PC in the firewall), you can use SCP with WINSCP or filezilla, but I think what you are trying to do is to remote copy the file from your PC to the EX9200 using regular installation, but it would be better to copy it to the switch and install it.
You can use ftp or SCP
request system software add ftp://<username>:<password>@<PC-IP>/pathname/package-name
request system software add scp://<username>:<password>@<PC-IP>/pathname/package-name
With the regular installation if you have the file in /var/tmp
request system software add /var/tmp/junos-install.tgz <re0 or re1>
You can use usb also, I'm adding procedure below:
https://kb.juniper.net/InfoCenter/index?page=content&id=KB12880
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Regards,
Franky