"Help to identify a power supply board burnt components"に関する回答R849 and R825 are resistors, and C811 is a capacitor. You can replace them by unsoldering them and soldering in replacements available online or from an electronic store, but you might want to consider why they burned up in the first place. The most likely thing is probably V810, the voltage regulator next to them on the board. It may have failed and caused the resistors and capacitors to fry. I’d look at the underside of the board and see if you can see any other scorch marks that might point you toward the cause of the problem.