The firing order is probably 1-5-3-6-2-4 but if you remove the plugs you can check with a finger over each plughole in turn. Rotate the engine in the correct direction with plugs out and distributor cap off until you feel some compression against your finger on no1. Continue rotating and you should get a similar effect in the next cylinder as appropriate in 1/3rd of a turn, I would expect it to be no 5, then 3 etc.
Having noted the direction of rotation of the distributor, continue until you are back to no 1 and stop at top dead centre, or as near as you can. The rotor arm will be pointing at where no 1 lead needs to be in the cap. You may need to slip the cap back on to check which lead position that is. Using the noted direction of rotation, replace all leads in the correct sequence.
This is a rough means and not to replace the correct method using the timing marks but will get you near enough to allow adjustment to run correctly.