How to directly save ai(illustrator image) to large size png or jpg?

There is no need to convert ai file to psd in order to make png or jpg. Open the file in illustrator. Just click on an empty area on the canvas and press delete key in keyboard to delete the canvas(do ungroup of images if every images gets deleted). Delete all the images but the one we need. Then click "export as" png or jpg from file menu option. In the next screen, you can select the resolution. Below 300ppi, there is 'other'. Click it and enter 712ppi. Thus you will get large crystal clear image.

Do this for all the images you need.