Is this possible with resistors? or will I need to buy a converter because I want to use a 5v relay
A lot of relay boards that you might get off of Ebay etc. use an optoisolator in the drive circuit and they work with the 3.3V Spark just fine.
If you are building your own relay circuit, you need a transistor and diode to drive the relatively high-current relay and prevent a voltage spike. Here is an example from Arduino land:
You can have 5V relay with an NPN transistor controlling it (with the diode please) as long as the 3.3V and 5V grounds are tied together.
a DC buck converter is around $3 bucks on aliexpress…2A and you can adjust to any voltage from any voltage
Talking from experience, the diode is required. Happend some time ago where my FETs were melting due to too large currents. Relay fixed it but leaving out the diode made my arduino corrupt the code all the time and eventually even the bootloader got corrupted.
Bottomline : always use a diode with a relay haha