This is a simple jewellery chain with a trace style chain and a spring ring lock.Each component are separate objects.
For Blender (native format) there is a simple Modifier rig for easy editing and fitting for your liking (Array and Path modifiers). The chains direction and lenght follows the path.
Parts are UV-unwrapped and are packed within the same UV-area.Vertice and Polygon count are stated with all the parts added together without the chain array and no Subdivision Surface on.