Replace everything in the circuit except the 3 A source by its Thevenin equivalent circuit and use the result to find V1
In the original schematic, is that a 24V source or a 24A source? The symbol does not match the label. I would interpret that symbol as a current source but it is possible that someone might use that as a voltage source considering you have a different symbol for the 3A current source.

Some people use an arrow to represent a rise in potential between two points on a schematic but I've never seen someone try to stick the arrow into a component symbol and try to call it a voltage source because it is confusing.

You interpreted it as a current source in your work, but if it is supposed to be a voltage source then the mistake is right there. Not that it's your fault. That's a really bad symbol.