Of course, you'll need 4 springs. Here are a few considerations when choosing upgraded 3D printer bedsprings:
The replacement springs are more rigid than the stock springs, increasing consistency between prints and reducing vibration.
The replacement springs are the same length as the original springs, meaning you shouldn't need to adjust your Z-axis endstop like you would with longer springs.
The replacement springs feature a flat top and bottom (vs. the stock springs' rounded top and bottom), resulting in less spring movement or shifting during and between prints.
After much research, I found these to be the best Ender 3 bed springs available on Amazon. They're under $10 with free shipping.
I recommend not removing the build plate completely since the back-right corner contains the heating element wiring. Instead, carefully lift each corner and replace each spring individually.
After all 4 springs have been replaced, reattach each adjustment knob. If you reattach any adjustment knob before all 4 springs are replaced, it will make it more difficult to replace each spring.
The new springs are a bit stiffer and feature a flat top and bottom, a definite improvement over the old springs.