There are many different applications for a pond that size.
The first is a skimmer. Installed outside the pond, keeps pump and plumbing hidden for better appearance, easy cleaning, catches floating debris in basket and fine debris with fiber filter mat
Submersible pump sits inside the skimmer or external pump can be used to pull water from skimmer.
Flow range of 1000 gph to 3500 gph.
Another is the Gravity type System which may be used with a waterfall or stream application. In the Gravity type filter, water is pumped in and exits by gravity back into pond
Mechanical and biological filtration using foam pad which can be easily cleaned without having to remove from filter
Thermometer and sensor to let you know when to clean are options in some systems.
Maximum flow 2300 gph
There are other types of systems available including systems that can be buried. If there are any pond builders or stores in the area just visit to see what is available. If you like to be creative there are many systems available that can be put together on a budget. I have found many pumps submersible and not and filter systems with pumps included from pools and hot tubs etc.
A stream and waterfall can also aid in filtration. You can build a stream using pond liner. Rocks and vegetation can be added for natural filtration. There are so many variations. One stream even had a bog built in to naturally filter the water. Ponds and the systems involved are many and varied.
The picture is from a pond I built. It consisted of a one large (1000) gal and a smaller pond (150) gal that were connected with a 25 foot stream with waterfalls, bog plants and fish. The small pond was built higher up and the water was pumped up from the big pond. No filters, just the pumps. Lasted for years and was completely natural.