What connector type.

[Doddy]

Those linked by Kitwn are compatible.

If OP wants a quick solution, rather than buying an uncompatible connector, another altogether better solution if you don't necessarily need to mate/unmate the relay board is to (easily) slide the black shroud of the connector on the relay board up on the pins (they are friction fit - not bonded) to remove the plastic from the 6 pins, then its an easy job to hold each pin one at a time an reflow the solder on the pad on the board. Decent temperature - you'll remove the pin in a second or two and you can clean the pad, then wire direct to board. It's not great, but these Dupont (or, more correctly mini-PV) connectors aren't brilliant since there's no mechanical retention of the mated connector beyond the sprung friction mechanism within the socket terminal.

If OP would prefer one of the alternative connectors - my advice would be to remove the Dupont (as above) and fit the corresponding, compatible plug. Not a bad idea if you want a more robust mechanism. That first one that DazP linked is a Molex KK-254 series - nice range of connectors with a strong mechanical retention mechanism - much superior to the Duponts. But don't mix-and-match - take my 50 life-years of experience of bad decisions on that one.

Edit: I've been to the shed - I hold consumable levels of KK-254s and Duponts - in fairness I can slide a Dupont socket down a KK-254 - and looking at the datasheets they each have a 0.64mm square pin, so actually not as bad as I make out above. The Molex pins are longer but are retained by the spring clips. But if you're ordering from Amazon just buy a Dupont jumper set to begin with.