1. Step 1: Create a new canvas with a width of 80cm and a height of 180cm, as shown below, and enter the following steps.

2. Step 2: After the above operation, if you want to know the number of pixels, just change the unit of length and width to pixels, as shown in the figure below, and enter the following steps.

3. Step 3: After the above operations are completed, if you want to print, the resolution should be above 150dpi; If you don't print, set 72dpi, as shown in the figure below, and enter the following steps.

4. Step 4: After the above operations are completed, if you want to print, change the "color mode" to "CMYK"; If you don't print, you should change the color mode to "RGB", as shown below. In this way, the problem is solved.