Since this is a paint job, you have to download the original helicopter once. here is the link: https://www.gtainside.com/gta5/helicopter/119413-eurocopter-as-365-air-ambulace-v2-add-on/

!!!!IMPORTANT!!!! You need OpenIV. here is the link to OpenIV: https://www.gta5-mods.com/tools/openiv

Installation Path: 
Please read the ReadMe for the original model