The 2 resistors below the regulator set the output voltage. On trace goes from those to the GND/ADJ pin of the regulator.
The tab is Vout on LM1117, so you can check with the continuity function of your multimeter, the tab should be connected to the center pin as well.
The pin to the right is the input pin.
If you can't find a *1117 , LM1085 or LM1084 should be pin compatible (they're 3A max for LM1085 and 5A max for the LM1084), they can work with higher input voltages (up to around 29v compared to most 1117 which cap at around 17v from memory) and they have same forward voltage drop (actually even better than 1117 chips at high currents, less than 1v at 1A, up to 1.3v at 3a compared to around 0.8v..1v at 0.8A for *1117 )
I keep using *1117 because they're literally made by lots of companies and they use various prefixes.