I claim the ornamental design for a power barrow, as shown and described.
FIG. 1 is a left-side view of the power barrow in accordance with the present design.
FIG. 2 is a bottom plan view of the power barrow.
FIG. 3 is a top plan view of the power barrow.
FIG. 4 is a back view of the power barrow.
FIG. 5 is a front view of the power barrow.
FIG. 6 is a front perspective view of the power barrow; and,
FIG. 7 is a back perspective view of the power barrow.
The broken lines in the figures are for the purpose of illustrating portions of the power barrow and form no part of the claimed design. The broken lines showing the outline of an engine are included for the purpose of illustrating environment and form no part of the claimed design.