You will only save the object, of course, so delete all measurements and other stuff.
Save your TCW file so you have the current version.
Select your object.
Under the Format menu, select Create Surface / From Solid.
Select File / Save As.
When the popup appears, go into Save as Type and select STP.
Save the file.
Close the file.
Select File / Open.
Make sure "Files of Type" shows "STP - Step Drawing"
Select the STP file you just saved.
Even though you converted it to a Surface before saving it, if the STP file has been created correctly, it will be loaded as a Solid. To verify this, select the object, then choose Format / Create Solid and verify that the options are greyed out (because you may not create a solid from a solid). You can also check the Create Surface sub-menu to verify that the "From Solid" option is not greyed out (because you have to have a valid solid object in order to change it into a surface).
TC Pro Platinum 2019, 2018, 2017, 2016 & 2015 (all with LightWorks & RedSDK) & V21
System: i7-5820K @ 3.30GHz, ASRock X99 Extreme4, 16GB DDR4-2133 RAM, Gigabyte GTX 970, Samsung NVMe SSD 950 (256GB), Windows 7 Pro (64-bit) SP1