Hi!
You should be able to upgrade directly to 11.4, please have a closer look at: http://www.juniper.net/techpubs/en_US/junos12.1x46/information-products/topic-collections/release-notes/12.1x46/topic-82934.html
I would recommend using the CLI when upgrading, it's not that complicated. Use an SFTP client like FileZilla to transfer the image to your /var/tmp folder, after that issue the install command:
request system software add /var/tmp/junos-srx1k3k-10.4R3.4-domestic.tgz no-validate no-copy
Replace to .tgz-file with the one you've downloaded. After successfull install, restart the device:
request system reboot