Threading cable through existing pex-like tubing
I agree with Solar Mike that a vacuum may work to pull a string, If the smurf tube or flexible nonmetallic conduit is 1 piece.  The nickname is from a kids carton where the characters are blue.

Having 9 or more flex lines going through a 4” makes me think this would not be 1 piece or the flex ends at the 4”, so you will need to try a fish tape.

A fish tape is a reel of steel or plastic that is used to push through a conduit, connect a wire and pull the wire back. The only problem(s) may be if the conduits stop prior to the 4” and the tape doesn’t go into the large pipe. The second possible problem is the 180 degree turn; depending on how tight this turn is, it may be tough getting a fish tape through depending on how far from the 4” pipe the flex conduits end.

If the smurf tube exits the 4” connect a vacuum and suck a string thru the tube a little plastic like a bit of bread wrapper on the end of the string helps the vacuum work.  Fish tapes come in different lengths from 25’ to 250’, it will need to be as long as the length of the conduit.
Just finished and saw your edit I think a tape or combination of tape and string are the paths forward.

Good luck