YOu can try to refer to below sample.
trn %>% DT::datatable(caption = "Transaction Table",
escape = FALSE, filter = 'top', rownames = FALSE,
extensions = list('ColReorder' = NULL, 'RowReorder' = NULL,
'Buttons' = NULL, 'Responsive' = NULL),
options = list(dom = 'BRrltpi', scrollX = TRUE, #autoWidth = TRUE,
lengthMenu = list(c(10, 50, 100, -1), c('10', '50', '100', 'All')),
ColReorder = TRUE, rowReorder = TRUE,
buttons = list('copy', 'print',
list(extend = 'collection',
buttons = c('csv', 'excel', 'pdf'),
text = 'Download'), I('colvis'))))