Hi Sheila,
Great question! Unfortunately, not all of those devices may be able to work with Alexa, but hopefully they are. The cable box is probably least likely to work with Alexa.
Here are the steps for your Sony TV (if your TV is supported!)

1. On the supplied remote control, press the HOME button.
2. Scroll down to Apps.
3. Under Apps, select TV Control Setup with Amazon Alexa app.
   • Note: You won’t find the TV Control Setup with Amazon Alexa app if your TV isn’t supported.
4. At the initial setup screen, click Next to continue. Then, follow the on-screen instructions to complete the setup.
5. In the Privacy Policy screen, select Agree.
6. In the Log in with Google screen, select Next.
7. Choose your Google™ account and go to the next step.
8. Select an easy-to-say TV name or create your own.
9. Complete the three last steps with Alexa.
   1. On your phone, set up the Android TV skill in the Alexa app .
   2. Choose the same Google account from Step 7 to link your accounts.
   3. Ask Alexa to discover your devices.
10. Select Done to exit from the setup. Otherwise, ask Alexa to try the other functions available.

If you go to Sony’s website, they have pictures detailing the setup.
The sound bar and cable box may have similar steps (depending on the brand and if Alexa is supported). You may need to visit the sites of those manufacturers.
Hopefully that helps!

-Daniel