Here we have another typo in the 1906 LDS edition; in this instance, the typesetter replaced “the Father” with “my Father”. The 1906 reading was not extended to any subsequent edition since that edition never served as a copytext.
Of course, either reading is theoretically possible here, although elsewhere in the book of 3 Nephi Jesus uses “the Father” much more frequently than “my Father” (123 to 10). Also in the book of 3 Nephi, Jesus refers to himself as going to “the Father” six times (including here in 3 Nephi 27:28) but only once as going to “my Father” (marked below with an asterisk):
Again, each reading is possible, but the is preferred. However, in the text immediately preceding this instance of “the Father” in 3 Nephi 27:28, there is an equal mixture of both types:
The sudden increased use of “my Father” seems to have led the 1906 typesetter to make the change to “my Father” here in verse 28. The critical text, as expected, will follow the earliest reading for each case of “the/my Father”, thus “the Father” here in 3 Nephi 27:28.
Summary: Maintain in 3 Nephi 27:28 the definite article the in the phrase “the Father”, the reading of the earliest textual sources.