I have a 24' piece of rope lighting and 2-12' pieces, are the 24' and the 12' connectable? The 2-12' pieces are.

If they are, it would be mentioned in the manufacturers instructions.

Is this what you have?

Can go up to 200 feet.

Buy a Hampton Bay 18 Ft. LED Rope Light Kit Specialty Lighting from The Home Depot

You can link this type of rope up to 200' so you should be good to go.