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Thanks for reaching out!
As you may know, the SR300 and the PMD cameras use different hardware and a different SDK, therefore, it is to be expected that functions that are on the PMD SDK are not present on the RealSense SDK and vice versa.
That being said, it is also important to mention that it doesn't mean that one can't do something the other one can but the way to do it may be different. For example, for pmdGet3DCoordinates, I'd suggest you to read this section https://software.intel.com/sites/landingpage/realsense/camera-sdk/v2016r3/documentation/html/index.html?doc_essential_coordinate_systems.html of the R3 documentation, it explains how to map coordinates including depth coordinates which could be the equivalent of the PMD function.
I suggest you to read the SDK R3 documentation so you can learn more about RealSense's capabilities and so you can find the appropriate way to complete your project. The documentation can be found at https://software.intel.com/sites/landingpage/realsense/camera-sdk/v2016r3/documentation/html/index.html.
I hope this information helps you,