Grab plugins from existing site into dev site

Hey All!

Background:

Client has an existing live site someone else built. Building them a new site that is responsive and better suited to serve their business needs.

Problem

Current live site for client has a few paid plugins that are necessary for their site rebuild, which I am doing. What would be the best way to grab those paid plugins (iThemes Security, &Easy Recipe Plus) and implement them in the development site I am building?

Thanks for any help you can provide!

Chris