ok. i will show you.
make new sketch on plane XY. than you draw lines using primitives. if you want symmetric so draw only half.
than use mirror feature to make it symmetrical.
than you accept the sketch. so you have the firs one
than create new sketch on plane XZ . draw line of needed dimensions. the line in second sketch is blue. the line with dotes you see above blue line is sketch number 1.
accept the sketch. so you have two sketches in different planes.
now use loft. and you will get wat you need.
at last picture you can see finished detail. but using loft and those lines you will get only surfaces. to make them thick i use feature thickness.