How do I convert an Illumina SNP Array genotype A/B coding into A/T/C/G using R?

Question

[sidtjn]

I want to convert a data set related to genome variation profiling and it only provided the information below:

Here are some information about the data set: GSE77508

I have tried looking for any sort of conversion table for that data set in the page itself and downloaded both files that they provided. Neither of them helped me. I have tried to look for 'HumanOmniExpress BeadChip' conversion table on Illumina's website but I couldn't find it. Is it possible to do this with the information that I have?