Typically a plan is much smaller in size than is the object or structure to be built. Converting 0.75 cm into meters and then dividing the result into 3 meters will give you a positive scale factor greater than 1.
Note that we can convert 0.75 cm into m by multiplying 0.75 cm by the conversion factor
1 meter
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100 cm
Please do this now.
Next, divide your result into 3 meters to obtain the scale factor.