Can I get a 2018 1040 tax form ?

Sorry 2018 is too old.   They only sell the last 3 years.  Even if you find the program you will not be able to update it or download any state programs you need.  You will have to go somewhere else like a local accountant.

Or If you have a simple return You can fill out the blank forms for free.

Here is the IRS 2018 Form 1040

https://www.irs.gov/pub/irs-prior/f1040--2018.pdf

And instructions  https://www.irs.gov/pub/irs-prior/i1040gi--2018.pdf

2018 Tax and EIC Tables https://www.irs.gov/pub/irs-prior/i1040tt--2018.pdf

IRS 2018  Schedules 1 thru 6 (only if needed)

https://www.irs.gov/pub/irs-prior/f1040s1--2018.pdf

https://www.irs.gov/pub/irs-prior/f1040s2--2018.pdf

https://www.irs.gov/pub/irs-prior/f1040s3--2018.pdf

https://www.irs.gov/pub/irs-prior/f1040s4--2018.pdf

https://www.irs.gov/pub/irs-prior/f1040s5--2018.pdf

https://www.irs.gov/pub/irs-prior/f1040s6--2018.pdf

TurboTax for 2018 is no longer available and is no longer supported. Some other tax software companies might still have 2018 available. Or you can go to a local tax professional.