BPMN Call Activity references an Activity defined in a process that is external to the current process definition. It allows you to create a reusable process definition that can be reused in multiple other process definitions. So if you want to reuse the entire process definition in another process, you need to consider Call Activity as the best component.
You can refer the below example how one process is being referenced in another process. The example is more dynamic assignment based on decision, instead you can configure your process directly in calledElement attribute instead of the expression.