He is trying to build one of those "stun guns" a kiddies electric shock toy.
A transformer will transform the voltage in the same ratio as the ratio of the turns on the windings.
For example, 90 turns on the primary, and 900 turns on the secondary will give a voltage ratio of 10 to 1.
ie 10 volts on the primary gives 100 volts on the secondary.
The transformer in the link is badly specified.
For each winding, the DC resistance is given, as is the "AC impedance" whatever that means, maybe the impedance measured at 1khz with an impedance meter.
What is not explicitly stated is the turns ratio.
My best guess at the turns ratio is that it will be close to the square root of the ratio of the primary and secondary "AC Impedances", I calculate (guess) the turns ratio as 16:1.
The maximum voltage that the transformer can handle will depend on the insulation on the wires and the way they are wound.
The transformer in the link is made as a small signal transformer and would normally only handle a few 10s of volts.
Hundreds of volts will breakdown the insulation.
JimB