In shemot 3:18 Adonai commands Moshe to tell the King of Egypt: 'nelacha-na derech shloshet yamim bamidbar venizbecha laHaShem Eloheinu'-'let us go a journey of three days into the wilderness, to sacrifice before HaShem our G-d'.Shemot 5:3 describes this event, but Pharoh refuses to let them go. This is why Moshe repeats this message in 8:23.
Question to what was this three day journey (a way of three yamim long) refering to? (to which place or event?)
After Pharoh let them go, the splitting of the Yam Suf etc. they arrive at the wilderniss, trafel for three days and arrive at Marah (Bamidbar 33:8).
Yom could also refer to a time period and the verse of 19:1 reads: BaChodesh Hashlishi.. after three months they arrived at the Midbar Sinai.
Pesach: the lamb kept for three days..