Impossible to answer due to the numerous factors that would be involved and no two journeys would be the same. However the link below provides information and a video of a journey recently made.
They did discover the way to travel underwater.
The time it takes for water to travel the Missouri River can vary significantly based on factors like flow rate and water conditions. On average, the river's flow rate is about 3 to 5 miles per hour. Therefore, it can take approximately 30 to 60 days for water to travel the entire length of the river, which spans about 2,341 miles from its source to its confluence with the Mississippi River.
The great Mississippi river is made entirely of fresh water.
Mississippi River
the Mississippi river
Mississippi river
At the confluence of the Missouri and Mississippi rivers, the Missouri River carries more water. Generally, the Missouri River has a larger discharge volume compared to the Mississippi at this point due to its longer length and larger watershed area. This makes the Missouri an important tributary to the Mississippi, contributing significantly to its flow.
Mississippi is bordered by the Mississippi River to the west.
The Mississippi River's watershed area, and rainfall.
The Missouri river and Mississippi river both travel through here, giving a lot of water to the land
Mississippi river
The body of water where the Mississippi river ends is the Gulf of Mexico.