Solo 401K and MEGA Backdoor ROTH

I have question for MEGA BACKDOOR ROTH IRA. How does it work.
I am Self employed and from prior year I have SEP-IRA, Traditional IRA, Roth IRA, Solo-401K account.

Here is what I am trying to do. I want to contribute to MEGA BACKDOOR ROTH IRA. I am contributing max to tax-deferred Solo 401K. To contribute remaining amount (say 20K) upto 56K limit, what I should make sure.


1. Transfer existing SEP-IRA, Rollover IRA and Traditional IRA to Solo 401K to make 
aggregate value of all Traditional IRA to zero.
2. Contribute to Solo 401K (up to tax deferred limit)
3A. Contribute non deductible 20K to Solo 401K Roth 
or
3B. Contribute 20K to Solo 401K and convert 20K to Individual Roth IRA.

Or let me know know if incorrect.


Thanks