Thanks - but my issue is I can't seem to find any information about the actual probes used in this dataset. Essentially I just have expression data and no rownames (ie featureNames). Not sure if this is buried somewhere in the GeneFeatureSet object itself that I'm missing or I'm meant to pull it somewhere else. For reference, this is how I pulled the dataset into R:
BiocManager::install("oligo")
library(oligo)
test_list <- list.files("/Volumes/GoogleDrive/My\ Drive/Bangelo_Lab/AD_Resilience_Project/Brain_Seq_MetaAnalysis/Datasets/Bulk/GSE39420/extracted/", full.names=TRUE)
test <- read.celfiles(test_list)