30mtr 20cm by 35

It looks like you're providing dimensions. To help you, I need to know what you want to calculate.

Are you trying to find the area of a rectangle? If so, please provide the length and width. For example, "Calculate the area of a rectangle with length 30 m and width 20 cm."

Or are you trying to find the volume of a rectangular prism (a box)? If so, please provide the length, width, and height. For example, "Calculate the volume of a box with length 30 m, width 20 cm, and height 35 cm."

Please clarify what you need!