Roth IRA Conversion

In the 2018 tax year, I was a full time student working part time.  During the year I earned about $

10k leaving me below the personal deduction for the year meaning no tax liability and a full refund of all my federal taxes paid. Further, I made the max contribution (5500$)  to a traditional IRA not knowing about the ROTH option. 

 

In the 2019 tax year, I converted my IRA to a ROTH and received my 1099-R for the distribution.

 

 I was unable to deduct the traditional IRA contribution because I had no tax liability in 2018. Should I have filed a Form 8606 in 2018 ?  Do I need a 8606 to prove my cost basis on the conversion in 2019?