You can use ls
with a specific pattern for example. For example:
some data.frames:
data.frame1 <- data.frame()
data.frame2 <- data.frame()
data.frame3 <- data.frame()
data.frame4 <- data.frame()
list(ls(pattern='data.fra*'))
[[1]]
[1] "data.frame1" "data.frame2" "data.frame3" "data.frame4"