No quick answer to this
You wrote "all equation".
There is a vast number of equations in existence and every time something new is found in the sciences it has to be mathematically modeled in an attempt to predict behaviour.
Consequently I should imagine the count is so vast that there is not anywhere that 'all equations' are recorded.
You could do web searches as one option or you could use third party software that has graphing capability.
It all depends on what the scope of your topic. Some scientific calculators will have graphing capability but this will have constraints.