Do we need to file I-485 after we received our immigrant visa?

No. You do need to pay the 165$ card production fee.

You do not need to file the 485. you will be entering the usa as a lawful permanent resident. not need to adjust your status. you will already have it. good luck

When you present yourself at a port of entry in the US with your immigrant visa, the border inspector will ask you questions. You do need to pay some fees before you come to the US. When the border inspector admits you into the US, that will result in a green card being produced and sent to you (in about 2-3 months after your entry). A Social Security Number will also be generated for you and sent to you as you likely have checked a box in one of the immigration forms asking for the SSN. You need to make sure that you have given the US government the correct address where you will get all your documents. If you do not get the SSN or the green card after 4 months, you need to follow up with the appropriate agency. US law also requires all aliens to notify the US government of a change in address within 10 days of the change. Generally, the Form AR-11 is used for the change of address for immigration services.

No you don't. You will get one in that mail provided that you pay the $165 fee for the green card on line.