There is only one specific ir codeset for your particular tv model, which is 1447.
Most dish remotes take 4 or 5 digits, not 3. If you require 3, you can try 447.
It is possible, however, that no matter what code is used, your remote will not be able to control the devices you wish to use it with. Cable/satellite/AV Component manufacturers include basic functionality for common devices at the time the remote is made, but are not able to provide coverage for every make and model, and are not able to update for every new device that comes out, so there is no guarantee of compatibility. This problem is compounded when using the low quality "off brand" products like proscan, which are notoriously incompatible with most remotes. In short, if this 1447 code does not work, then your dish remote is simply not capable of working with this particular tv.
Your best option may be to purchase a more robust, true universal remote to control all of your devices, such as a logitech harmony (click here for example) that will work for all of your devices. It is programmed through an easy to use software program on your computer, which downloads the most up to date remote and device codes from the internet, so it is virtually guaranteed to work with all equipment. It will also give you easy to use macro functionality, so you can press a single button to watch a movie for example, and it will turn on the dvd player, tv, and surround system, tune to the correct inputs on the tv, and start the movie playing, etc. Because of the online database with specific codes for each model, this type of remote has much greater functionality than the basic universal remotes (including the one that came with your system.)
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I am an independent technician and I've spent my personal time, unpaid, in a good faith effort to assist with the question for which you solicited my services. I am only paid for my efforts when customers such as yourself leave positive feedback for my work. Again I apologize there is not a better outcome here, though this is really beyond either of our control. I do hope you’ll consider leaving a positive rating for me, rather than “shoot the messenger”, so that I may get credit for my time spent in good faith to answer your question accurately.