I bought a new laptop Dell G15 5530, it ran into a problem , i had to reset laptop, now alien wear software is missing

All the software should be available for free downloading from Dell on the G15 5530 support page. You can either allow the site to scan your PC automatically and see if it offers the Alienware apps. 

Or, click Find Drivers on that same page. When that opens, choose Applications from the list of options and you should see a link to download Alienware Command Center 6x - Full Installer for Alienware/Dell G Series System.