Can this transfer or NAS backup finish inside the available window?
Convert bits and bytes first, then use the slowest sustained network, source-read or destination-write stage. Add an editable small-file cost and verification pass; advertised link speed alone is not a completion estimate.
Method
Planned time is data divided by the bottleneck goodput plus file-count overhead, repeated for verification when selected. All efficiency and per-file values are editable assumptions and should be replaced by a short benchmark.
Important limitation
Caching, compression, deduplication, encryption, latency, errors and changing workloads can move the result. The planner never scans a LAN, signs in to a NAS or starts a transfer.